In the example "Longitudinal Study with a covariate", the model uses Program A as the reference category, this means that the coefficients for Programs B, C, and D are compared to Program A.
The coefficient for "Program_B" is significant (p-value = 0.0070394), indicating that Program B has a significantly different effect on weight loss compared to Program A, averaged over all weeks.
The interaction term "Program_B:Week" is not significant (p-value = 0.68521), meaning there is no significant difference in the effect of "Week" on weight loss between Program B and Program A. Each interaction term specifically compares the effect of "Week" for that program to Program A, the reference category.
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